Visualization of the gas permeation in core–shell MOF/Polyimide mixed matrix membranes and structural optimization based on finite element equivalent simulation

•Two MOFs with adverse core–shell structure were designed.•ZIF-67@ZIF-8 based MMMs exhibited the best gas separation performance.•A simplified equivalent simulation was adopted to analyze gas separation.•The simulation well matched the experimental results after adjustment.•The gas transport inside membranes was revealed by this visual simulation.